No special access issues
EVERYTHING IS ILLUSTRATED AND INDICATED IN THE PDF TOPO HERE :
https://sybed.gumroad.com/l/toponaviteau
Rocher de Naviteau is located just between the road "chemin des aires prolongés" and the departmental road M65, in Castelnau-le-Lez.
You can go there either in car/van 🚙 (you can easily park along the road "chemin des aires prolongés"), or in autobus 🚐 with the line 35 or 36. From Montpellier's center, it takes around 30 minutes to get there in both ways.
Both buses leave/pass by the tramway stop Charles de Gaulle, the 35 has two stops ("Balestrier" or "Les Aires") that are at 100 meters from the trail access, whereas with the 36 stop ("Jean jaurès"), you'll have to walk around 10 min on the small town roads to get to the trail.
! The trail is sometimes hard to find. !
Due to the quick growth of the vegetation, the trail can be hidden.
It is on the (north) flank of the cliff/wall, and you should acces it by going through the bushes when you're near the house number 177 chem. Aires prolongés. You should quickly see a small, old castle ruin belon : the trail is at its left.